Spencer Trask, a venture capital firm that has invested more than $650 million of seed capital in start-up firms, is coming under fire from unhappy clients who say the firm’s top execs are keeping the best deals to themselves, The Post has learned.

The 119-year-old company came under the control of Kevin Kimberlin, a former executive of the scandal-plagued Wall Street firm D.H. Blair, in 1991 when he bought a controlling stake.

Clients say the firm has been a downhill ride for them since, as Kimberlin, now chairman, turned the VC firm into a money-making machine for himself – but no one else.

“The clients don’t get the best deals,” said one disgruntled millionaire investor, whose negative sentiments were shared by six other investors who talked to The Post.

“Kevin keeps them to himself. When he makes money, he hypes it as if it were a big win for all of us, but he’s the only one making any money. I haven’t really made any money yet.”

This investor, who like the others did not want his name disclosed, said he became a Spencer Trask “angel investor” in early 1998 and has subscribed to six of the 12 private placements offered to him.

He, like other investors, has a net worth of more than $1 million, investable assets of at least $200,000, and has promised to put $12,500 or more into each of at least six private placements per year.

Another client, a lawyer, told The Post, “they hype and promise great returns, but it ends up a major disappointment.”

The investors are particularly angry about three private placement deals: Ciena Corp., Next Level Communications and SmartServ Online. They said they were not offered a piece of these successful deals while Kimberlin was a seed investor in all three.

Kimberlin told The Post he personally made an investment in each of the three, but blamed the companies for not opening up for additional investment from his clients.

“In the Ciena situation, I did get an opportunity to be a seed investor,” he explained. “But at the time of the second round of financing, there were quite a few institutional investors on board, and Ciena decided it did not want any other investors. I can’t dictate what a corporation does, but it’s true that Ciena was not offered to Spencer Trask shareholders.”

He said Next Level and SmartServ were similar situations. On its Web site, Spencer Trask highlights the Ciena deal as one of its biggest successes.

“We spearheaded the initial financing of Ciena Corporation, possibly the most successful venture investment of modern times,” states the Web site. “It was the largest IPO by a technology company in history when it raised $135 million.” The Web site goes on to say that Ciena’s post-IPO valuation of $6 billion generated a return of 28,000 percent for investors who participated in the first round of financing.

But only Kimberlin’s personal portfolio registered that particular gain.

Kimberlin’s bio – also on the site – omits his background with the defunct D. H. Blair, another source of bitterness with clients who believe that history should have been disclosed.

Last week, 15 officers from D.H Blair – including its three top execs – were indicted on charges that they ran the securities firm as a corrupt enterprise. They were accused of scamming 60 investors out of tens of millions of dollars.

“I left [Blair] over 10 years ago, so I don’t see it as relevant,” said Kimberlin.

Clients complain that even when Spencer Trask has got them in deals, it was only after Kimberlin got in at a lower price. That, they say, is what happened with Myriad, another “success” touted on Spencer Trask’s Web site.

“He’ll put in seed money and then go to another round of financing and that one goes for a lot more money,” said one client. “He says he’s taking on extra risk by going in early, but by the time he offers it to me, it’s a much higher valuation, which means we sometimes can’t actually make money at the IPO like he does.”

Kimberlin said that’s the nature of the business.

“The first stage is seed capital, where there’s a lot of risk and a lot of uncertainty about whether an idea will really work in this world,” he said. “That is the stage where I typically make an investment. After you get a little more flesh on the bones, you do a first-round private placement and bring in more investors. That’s what Spencer Trask does. If you do it right, the IPO is at an even higher price. But it doesn’t always work out that way.”